Caspian Tern / Taranui

The Caspian Tern is a cosmopolitan species found in many localities throughout the world. It is thought to be a recent coloniser to New Zealand with sub-fossil remains found rarely and sightings not recorded by early naturalists until about 1860. Their population has increased slowly since then and now numbers around 1300-1400 pairs. Although widespread throughout the country they are still considered uncommon with numbers appearing to have declined since the 1990s.

Their conservation status is Nationally Vulnerable protected native species.

Caspian tern in breeding plumage. Photo credit Bevan Walker.

The Caspian tern is the largest of all the tern species found in New Zealand. It has a 1 metre wingspan and is roughly the same size as a black-backed gull. Their upper plumage is silver-grey with white below and smudgy black wing tips. During the breeding season adult birds have a distinctive black head cap to below the eye, which at other times becomes speckled with white and the edges less defined. Their bill is bright red and legs black. When flying they can often be heard emitting their loud, distinctive and repetitive harsh ‘kaa, kaa’ call.

Caspian terns occupy a variety of sheltered bays and harbours around coastal New Zealand but can also be seen regularly at inland lakes and rivers in Canterbury and the central North Island. They breed mainly on coastal sand spits and shell banks and occasionally on braided rivers and inland lakes. Most nest in large loose colonies of up to 100 pairs, but many nest singly or in association with other gulls (both red-billed and black-backed) and white-fronted terns.

Caspian tern in non-breeding plumage. Photo credit Bevan Walker.

One or two Caspian terns are seen regularly feeding in the shallow waters of the Whangamatā Harbour and resting at the high-tide roost site adjacent to the Beach Road Reserve. They seek small surface swimming species such as yellow-eyed mullet, piper and smelt by flying up to around 15 metres above the water surface.

When their prey is sighted they plunge-dive steeply, often completely submerging themselves in the process. If successful they quickly take-off and swallow the fish while in flight. They are also known to feed on schooling fish along with other sea birds but are usually solitary feeders.

— John Adams. Whangamatā Harbour Care.